There are now high requirements for engines to discharge as little as possible of substances which are harmful to the environment, while at the same time it is desirable to lengthen the interval between servicing operations. For an engine to achieve this, the oil used for its lubrication and cooling has to meet high requirements. A properly functioning combustion engine consumes less propellant and discharges a smaller amount of substances which are harmful to the environment. To enable for example a combustion engine to discharge smaller amounts of pollutants it is desired to increase the pressure and temperature at which the combustion takes place. This involves still higher requirements for the engine's components, inter alia the motor oil. Engines of heavy vehicles are subject to particularly severe stresses in that they have to provide a very large amount of power to enable the vehicle to travel and carry its cargo in a desirable way.
Motor oil is used as lubricant in combustion engines. Contact with acid combustion gases acidifies this oil, which is thus degraded and may become corrosive, with consequent adverse effects both upon the its tribological (lubricating) characteristics and upon the surface layers of the lubrication system.
Various additives are used to improve motor oil characteristics, comprising inter alia acidity-regulating (buffering) additives, but also viscosity-regulating, anti-oxidant and wear-inhibiting additives to make it possible to cope with the high pressures and temperatures at which the engine operates. These additives are consumed over time and when their amount in the oil reaches a certain level the oil has to be changed. The consequences of additive consumption include impairment of the oil's tribological characteristics, and in the worst case the oil may cause corrosive wear of the components with which it comes into contact. The additives are important to enable the oil to perform its function in a desirable way but they also lead to increased levels of soot in the exhaust flow. Too high soot contents in the exhaust gases result in greater load on exhaust-cleaning components, e.g. the particle filter.
Ion exchangers are solid materials (insoluble matrices), often with a carbon/silicon-based fundamental structure, which have the ability to bind positive or negative ions (cation exchangers and anion exchangers respectively). A cation exchanger can capture positive ions of one kind while at the same time releasing positive ions of another kind. Similarly, an anion exchanger captures negative ions of one kind while at the same time releasing negative ions of another kind. The ions captured by/released from an ion exchanger are called counterions.
There is today a new technology, COT (clean oil technology), which continuously cleans the oil during operation. The system takes the form of a bypass duct and the oil passes not only through a fine-mesh particle filter which removes very small solid pollutants, but also through a vaporisation unit which separates liquid pollutants which are of lower vapour pressure than the oil. This technology does however not deal with the increasing acidity of the oil.
WO 2004/094381 A1 describes acidity regulation and monitoring of lubricating liquids used in air compressors of screw or centrifugal type. Lubricating liquids used in such a compressor are not subject to as aggressive an environment as motor oil and therefore do not have such a large content of additives or harmful particles. They are however subject continuously to a certain acid load and WO 2004/094381 A1 proposes that this be dealt with by using anion exchangers.
GR1004835B1 describes filtration and acidity regulation of motor oil by ion exchangers. The acidity regulation takes place in a separate device outside of the vehicle and the oil needs to be as clean as possible, i.e. with no additives or pollutants remaining in it. This means that the additives, which are expensive and distinguish a good motor oil from a less good one, are removed, but so too at the same time are other additives to the oil. The result will be a clean and relatively inexpensive bulk oil.